JP2009195977A - Automatic welding control method and automatic welding apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic welding control method and an automatic welding apparatus in which a visual sensor for welding and a laser beam sensor are mounted on one sensor head, an ideal welding control system is constructed by supplementing the visual sensor for welding and the laser beam sensor with each other without considerably impairing the accessibility of a welding torch to a workpiece, and a preliminary teaching of a groove shape before the welding is unnecessary. <P>SOLUTION: The welding control is performed to a workpiece 10 to be welded by alternately functioning a visual sensor and a laser beam sensor during the welding operation by using a compound sensing system consisting of the laser beam sensor composed of at least a laser beam projector 30, a filter 32 for the laser beam sensor, and an image pickup camera 36, and the visual sensor composed of at least a filter 34 for the visual sensor and the image pickup camera 36. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an automatic welding control method and an automatic welding apparatus, and in particular, an automatic welding control method capable of performing high-precision welding control using a welding laser sensor and a welding visual sensor in combination, and The present invention relates to an automatic welding apparatus employing an automatic welding control method.

  When performing arc welding, a welding sensor and its vicinity are used by using a visual sensor with a CCD camera, etc. to adaptively control the welding conditions so as to properly maintain the welding line copy of the welding torch and the size of the weld pool. Images are taken.

  The inventor has proposed a visual sensor for welding in Patent Document 1 for capturing an object such as a molten pool or an arc.

  In addition, in the patent document 2, the inventors photographed the weld pool and its vicinity with a visual sensor, extracted the outline of the weld pool from the photographed image, and extracted the singular point of the weld pool from the extracted contour. Then, the presence / absence of the scanning position deviation of the electrode with respect to the welding line, the scanning position deviation direction and the target positional deviation amount are calculated from the extracted singular point, and the welding torch is calculated based on the calculated electrode positional deviation amount and the scanning position deviation direction of the electrode. A technology to control the position of the camera is proposed.

  Furthermore, one of the inventors, in Patent Document 3, photographed the weld pool of the member to be welded and its vicinity with a visual sensor, extracted the contour of the weld pool from the photographed image, and extracted the weld pool tip width from the extracted contour. And calculating the route gap change amount based on the calculated weld pool tip width, and calculating the torch swing width control amount and the welding speed control amount based on the calculated route gap change amount. We have proposed a technique for controlling the swing width and welding speed by the control amount of the torch swing width and welding speed.

  In addition, one of the inventors extracted a left and right end image of a torch swing from an image of a weld pool and its vicinity photographed by a visual sensor in Patent Document 4, and extracted left and right end images. To create a composite image having a virtual weld pool image, calculate the distance between the left end point and the right end point of the virtual weld pool image as a swing width feature amount, and torch swing pattern with respect to groove width variation The tracking (adaptive) control is appropriately performed, and the distance from the tip center point of the electrode image to the center point of the left end point and the right end point of the virtual weld pool image is calculated as the swing center feature amount, and the calculated swing A technique for appropriately performing groove centerline scanning control using the center feature is proposed.

  Patent Document 5 calculates the height of a tacking bead by imaging the welding situation and calculating the groove shape and the height of a tacking bead placed therein by image processing. On the other hand, the optimum welding conditions according to the bead height on the start and end portions of the tacking bead and the tacking bead portion are stored in a database in advance, and this is the bead height at each tacking position. A technique is disclosed in which optimum welding conditions are selected from a database and welding is performed at the value.

JP 2006-7303 A JP 2006-55858 A JP 2006-281282 A JP 2007-185700 A Japanese Patent Laid-Open No. 11-5164

  The advantage of using a visual sensor for welding is, for example, that the weld pool and the welding electrode directly above it can be directly photographed during welding, and the position of the welding electrode in the groove can be directly detected through the image. Even if the bending curve of the welding electrode changes, the groove tracing accuracy of the welding torch can be accurately performed, and the change of the groove shape can be estimated indirectly in real time, so that the welding conditions can be adaptively controlled. It is in.

  However, since the molten pool itself is a fluid, it is susceptible to various disturbances, and at the same time, the brightness of the molten pool image easily changes due to the influence of arc light, so the stability of the molten pool image is not so good. Therefore, there is a problem that the measurement accuracy of the groove dimension change amount is not so high and cannot be expected.

  Also, if there is a temporary bead in the groove, even if the visual sensor can detect the presence or absence of the temporary bead, the welding arc is usually already detected when the visual sensor detects the presence or absence of the temporary bead. Even if the welding conditions can be changed instantaneously at this time, the welding defects remain at the start and end points of the tack bead because they are climbing on the tack bead or away from the tack bead. There was a fear.

  In order to solve such problems, a method of simultaneously using a welding laser sensor is conceivable. In general, a welding laser sensor irradiates a groove in front of a welding position with a flying spot laser beam or a slit laser beam, takes a light-cut image of the groove with a camera, and changes the groove shape through image processing. Is detected directly. Therefore, high detection accuracy can be obtained relatively easily by using an appropriate camera, filter, image processing technique, and the like. Another advantage of using a laser sensor is that the welding conditions can be controlled with feedforward control. For example, if there is a temporary bead in the groove, the presence or absence of the temporary bead can be detected in advance by the laser sensor. Therefore, when the arc passes through the temporary bead, the welding conditions are changed in a timely manner. It is possible to perform welding without leaving a welding defect at the start point and the end point of the tacking bead.

  Laser sensors for welding are often used for groove tracking control, but the method that recognizes them in advance before melting cannot respond to changes during melting because there is a time lag between measurement and control. There is a problem that it is difficult to use in copying control. Further, even in the case of straight groove tracking control, it is necessary that the relative position between the welding electrode and the laser sensor is fixed or the change amount thereof can be grasped in real time. This is because in a laser sensor, since the welding electrode is not in the field of view, the relative position between the sensor and the electrode cannot be measured in real time. Therefore, if there is a random variation in the relative position between the sensor and the electrode, there is a problem in that the variation remains as an error in groove tracking control.

  As described above, the visual sensor for welding that captures light that emits light, such as a molten pool, an arc, and the like, and the laser sensor that can capture any shape because it is reflected light have their respective strengths and weaknesses. Therefore, if both are used simultaneously, they can complement each other and an ideal welding control system can be constructed. However, if both are used at the same time, two sensor systems are required, which is expensive, and at the same time two sensor heads must be mounted in the vicinity of the welding torch. There was a risk of serious damage.

  The present invention has been made to solve the above-mentioned conventional problems. An automatic welding control method and an automatic welding method that can eliminate the prior teaching of the groove shape before welding by using a combined sensing system of a laser sensor and a visual sensor. It is an object to provide a welding apparatus.

  The present invention uses a combined sensing system of a laser sensor including at least a laser projector, a laser sensor filter and an image capturing camera, and a visual sensor including at least a visual sensor filter and an image capturing camera, on an object to be welded. The above-mentioned problem is solved by an automatic welding control method characterized in that welding control is performed by causing a visual sensor and a laser sensor to function alternately.

  The composite sensing system may include a single image capturing camera in which a filter for a laser sensor and a filter for a visual sensor are interchangeably functioned.

  A state in which the composite sensing system is used as a laser sensor in a state in which the welding arc is expected to be measured, sensor information is measured and stored in a welding in-process, welding is performed by feedforward control based on the information, and a welding arc is expected Therefore, it can be used as a visual sensor to detect changes in the welding situation that occur during welding by welding in-process, and to perform feedback control in real time based on such information.

  Here, when the change in the welding situation that occurs during the welding is a deviation in the groove tracing of the welding torch, the deviation is related to the positional relationship between the welding electrode (also referred to as a wire) that is visual sensor information and the molten pool. Changes can be detected and feedback controlled in real time.

  Alternatively, if the change in the welding situation that occurred during the welding is a change in the appropriate amount of welding required during the first layer welding, the welding is performed based on the height change of the weld pool during the first layer welding, which is visual sensor information. An additional correction amount of the amount can be obtained and feedback control can be performed in real time.

  The present invention also provides a laser sensor including at least a laser projector, a laser sensor filter and an image capturing camera, a visual sensor including at least a visual sensor filter and an image capturing camera, and the visual sensor and the laser sensor during welding. A means for alternately functioning in a state in which a welding arc is expected and a state in which a welding arc is expected, an image processing device that calculates welding control data from images obtained by the laser sensor and the visual sensor, and a welding torch are provided. An automatic welding apparatus comprising an automatic welding machine and means for controlling the automatic welding machine based on the welding control data is provided.

  Here, it is possible to provide a single image capturing camera in which the laser sensor filter and the visual sensor filter function so as to be interchangeable.

  Further, the image photographing camera, the laser projector, and the welding torch are all attached to the same beam, and the image photographing camera can photograph the light projecting position of the laser projector and the welding position of the welding torch.

  In the composite sensing system according to the present invention, a visual sensor that captures light emitted from a molten pool, an arc, and the like and a laser sensor that can capture any shape by reflected light are caused to function alternately during welding. In order to realize this, the sensor head of the composite sensing system is attached to, for example, one slider, and this slider is moved back and forth along the welding direction.

  For example, when the slider comes to a position where it looks just before the front welding arc, this combined sensing system is used as a laser sensor, and sensor information such as groove dimensions, groove position, and temporary bead in the groove is displayed. It is measured and stored in the welding in-process, and based on these measurement data, welding conditions, groove copying, and the like are feedforward controlled.

  On the other hand, when the slider comes to a position where it looks just before the rearmost welding arc, for example, this composite sensing system is used as a visual sensor, and an error in feedforward control by the laser sensor, for example, the groove tracing of the torch. Then, a change in the groove width due to the welding heat or a change in the amount of welding due to the random outflow of the molten metal into the gaps is detected by welding in-process, and feedback control is performed in real time based on the measurement data.

  Therefore, an ideal welding control system can be constructed by making the best use of each field of vision sensor and laser sensor and complementing each other.

  Furthermore, since the visual sensor and the laser sensor are combined, only one sensor head and measurement system are required, and image processing can be handled by software, so that the accessibility of the welding torch to the workpiece may be impaired, and the hardware of the image processing apparatus Is not complicated.

  Furthermore, prior teaching of the groove shape before welding is not necessary.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a state where an embodiment of the composite sensing system according to the present invention is used as a laser sensor during welding, and FIG. 2 shows a state where it is also used as a visual sensor during welding.

  The present embodiment includes a laser projector including a laser projector 30, a laser sensor filter 32, and an image capturing camera 36, and a visual sensor including a visual sensor filter 34 and the image capturing camera 36. The image capturing camera 36 includes: The laser sensor filter 32 and the visual sensor filter 34 are configured as a single image capturing camera functioning interchangeably.

  The laser projector 30 and the welding torch 22 are fixed to one end (left end in the figure) of a beam 40 provided on the welding head 20, and the sensor head including the image capturing camera 36 is welded on the beam 40 in the welding direction (in the figure). It is attached to the tip (right end in the figure) of the slider 42 that can move back and forth along the right direction.

  The back-and-forth movement of the slider 42 is interlocked with the swinging motion of the welding torch 22, and when the torch 22 passes the swing center, the slider 42 is in the most extended state, and the torch 22 Is reached, the slider 42 is in the most contracted state. The means for driving the slider 42 may be an air cylinder (not shown), for example. A motor or an electromagnet can also be used.

  On the other hand, when the torch 22 does not swing, the operation of the slider 42 may be determined voluntarily.

  Switching between the laser sensor and the visual sensor of the composite sensing system is synchronized with the operation of the slider 42. That is, when the slider 42 is extended to the maximum, the laser projector 30 is quickly irradiated and the camera 36 is photographed. The composite sensing system at this time functions as a laser sensor.

  However, when the composite sensing system is used as a visual sensor or a laser sensor, it is desirable to use a bandpass filter suitable for each. For this purpose, a dice filter set 31 that can rotate 90 degrees is installed in front of the camera lens. The movement of the filter set 31 is synchronized with the slider operation. When the slider 42 is in the most extended state, the laser sensor band-pass filter 32 is rotated in front of the camera 36. When the slider 42 is in the most contracted state, the visual sensor The band pass filter 34 is rotated in front of the camera 36.

  As a means for rotating the dice filter set 31, for example, an electromagnet or a motor may be used.

  In the figure, 10 is a workpiece, 24 is a welding electrode, 26 is a welding condition control device, 28 is a remote control, 30S is a laser (slit) light for illumination, 38 is an image processing device, and 52 is a composite sensing system control device. .

  FIG. 3 shows the measurement procedure of this embodiment. The left side is a measurement procedure when used as a laser sensor as shown in FIG. 1, the right side is a measurement procedure when used as a visual sensor as shown in FIG. 2, and switching is controlled by a measurement mode signal (step 102). .

  When this composite sensing system is used as a laser sensor, as shown in FIG. 1, the slider 42 is advanced by the composite sensing system control device 52 and at the same time the filter set 31 is rotated by 90 ° to obtain a (band pass) filter for the laser sensor. 32 is installed in front of the camera 36. The combined sensing system is now a laser sensor.

  Here, the welding control is first performed by a feed forward method based on the laser sensor information. The control is mainly adaptive control of welding conditions. In other words, the welding conditions (welding current, voltage, welding speed, torch swing width, swing) are determined based on the presence or absence of a temporary bead in the groove obtained from the laser sensor, the groove width, the groove depth, and the root gap. The amount of correction of the end stop time and the like is obtained, and these are added to the reference welding conditions to perform feedforward control of welding (steps 104 to 114).

  FIG. 4 is a schematic diagram of a laser sensor light cut image of a V-shaped groove photographed when the composite sensing system is used as a laser sensor. In general, the welding arc 25 does not enter the field of view of the camera 36 at this time, and image processing is easier with only the cut image of the laser slit light 30S. Therefore, it is desirable to select the irradiation position of the laser slit light 30S at a location 20 mm or more away from the front of the arc.

  If this V-shaped groove laser beam cut image is subjected to image processing by the image processing device 38, first five singular points SP1 to SP5 can be found. Here, SP1 is a groove upper end point of the left side plate, SP2 is a groove upper end point of the right side plate, SP3 is a groove lower end point of the left side plate, SP4 is a groove lower end point of the right side plate, and SP5 is a backing center point. is there. The feature values SV1 to SV8 can be obtained from these singular points. Here, SV1 is a groove width, SV2 is a root gap, SV3 is mistaken, SV4 and SV5 are back and left gaps, SV6 and SV7 are left and right plate thicknesses, and SV8 is a groove depth. Further, the center position of the groove can be obtained from SP1 and SP2 or SP3 and SP4, and the sectional area of the groove can also be obtained from SP1 to SP5.

  On the other hand, a schematic diagram of a laser beam cut image of the temporary bead portion in the groove can be represented in FIG. Here, five singular points SP1 to SP5 are similarly obtained. Therefore, if the feature amounts SV1 to SV8 are obtained from these and compared with the feature amount of the groove having no temporary bead, the presence or absence of the temporary bead can be known. For example, one feature of the temporary bead portion is that the groove depth SV8 is shorter than the plate thickness.

  Based on the groove width obtained by using the combined sensing system as a laser sensor and the center position data of the root gap, the groove tracing of the welding torch 22 can of course be performed. To correct based on the information obtained.

  When the composite sensing system is used as a visual sensor, as shown in FIG. 2, first, the composite sensing system control device 52 moves the slider 42 backward to the left in the figure, and the welding torch 22 that has arrived at the swing end is taken into the camera. The position 36 is expected. At the same time, the filter set 31 is also reversely rotated by 90 °, and the visual sensor filter 34 is installed in front of the camera 36. Thus, the composite sensing system becomes a visual sensor, and if the camera 36 is photographed at this timing, a molten pool and a wire image can be taken (steps 122 to 128 in FIG. 3).

  For example, the methods described in Patent Documents 2 to 4 can be used as processing methods for the taken molten pool image and wire image. That is, as described in Patent Document 2, as shown in FIG. 6, the weld pool 10 and its vicinity are photographed with a visual sensor, and the contour 13 of the weld pool 12 is extracted and extracted from the photographed image. Four singular points of the left end point LP and the right end point RP of the molten pool 12 and the left end point FLP and the right end point FRP of the tip of the molten pool 12 are extracted from the contour 13. The difference between the lengths of the two diagonal lines L1 and L2 of the quadrangle 14 formed by the four extracted singular points is calculated, and the electrode 24 is copied with respect to the weld line from the calculated difference ΔL between the two diagonal lines. The presence / absence of the positional deviation, the scanning positional deviation direction, and the scanning positional deviation amount are calculated, and the position of the welding torch 22 is controlled based on the calculated positional deviation amount of the electrode 24 and the scanning positional deviation direction (step 130). As a result, it is possible to perform highly accurate welding line scanning control.

  Alternatively, as described in Patent Document 3, as shown in FIG. 7, the molten pool 12 and its vicinity of the workpiece 10 are photographed with a visual sensor, and the outline 13 of the molten pool is extracted from the photographed image and extracted. From the contour 13, the left end point FLP and the right end point FRP of the molten pool tip are extracted. The molten pool front end width W is calculated from the coordinates of the extracted left end point FLP and right end point FRP of the molten pool front, and the route gap change amount ΔW is calculated from the calculated molten pool front end width Wo. Based on the calculated change amount ΔW of the route gap, the control amount Wt of the torch swing width and the control amount Vw of the welding speed are calculated, and the swing width is calculated by the calculated torch swing width Wt and the control amount Vw of the welding speed. The welding speed is controlled (step 130). Thereby, regardless of whether it is TIG welding or GMA welding, a good back bead shape and bead quality can be stably obtained even if the root gap, the backing gap, or the mistake is changed.

  Alternatively, as described in Patent Document 4, as shown in FIG. 8, images 16R and 16L of the left and right end portions of the torch swing are extracted from the weld pool 12 of the workpiece 10 taken by the visual sensor and the vicinity thereof. Then, the extracted left and right end images 16R and 16L are combined to create a composite image 18 having the virtual weld pool image 12 ', and the distance between the left end point LP and the right end point RP of the virtual weld pool image 12' Is calculated as the swing width feature amount, and the follow-up (adaptive) control of the torch swing pattern with respect to the groove width variation is appropriately performed. Further, the distance from the tip center point WP of the electrode image 24 to the center point of the left end point LP and the right end point RP of the virtual weld pool image 12 ′ is calculated as the swing center feature value, and the calculated swing center feature value is used. Thus, groove center line scanning control is appropriately performed (step 130). In the figure, 11 'is a virtual groove. Thereby, even if a route gap, a backing gap, or a mistake is changed, a good bead shape and bead quality can be stably obtained.

  In FIG. 9, the example of the welding control method based on each information of a laser sensor and a visual sensor is shown.

  Here, the welding control is first performed by a feed forward method based on the laser sensor information. The control is mainly adaptive control of welding conditions. In other words, the welding conditions (welding current, voltage, welding speed, torch swing width, swing) are determined based on the presence or absence of a temporary bead in the groove obtained from the laser sensor, the groove width, the groove depth, and the root gap. The amount of correction of the end stop time and the like is obtained, and these are added to the reference welding conditions to perform feedforward control of the welding.

  Of course, the groove tracking of the welding torch can be performed based on the groove width obtained from the laser sensor and the center position data of the root gap, but the actual deviation of the scanning control was further obtained as a visual sensor. Correct with feedback based on information.

  The visual sensor is mainly used for groove tracking control of the welding torch. However, since there are fluctuations in the backing gap and changes in the amount of welded molten metal that has entered the gap during the first layer welding, feeding by teaching playback data based solely on data information obtained from the laser sensor before welding is performed. Forward control alone may be difficult to maintain a high quality first layer weld bead. Therefore, based on the height of the weld pool obtained from the visual sensor during the first layer welding (see Patent Document 3 and Patent Document 4), an additional correction amount of the welding amount is obtained, and feedback control is performed in addition to feedforward control. To do.

  In an emergency, manual control can be performed by the remote controller 28 at hand. For example, when an emergency stop is detected or a control deviation is detected from the monitor, manual correction can be performed in-process.

  As a result of the welding control based on the combined sensing system described above, it is possible to achieve full automation of the welding process, and at the same time, even if the actual groove shape deviates greatly from the standard shape, for example, a steel plate backing is attached. In the case of the groove, the variation in the root gap was 2 mm to 12 mm, and it was confirmed that a uniform and high-quality weld bead could be obtained regardless of the presence or absence of a tack bead.

  In the present embodiment, the image camera 36 is fixed to the tip of the slider 42, and the position of the image camera 36 is fixed by sliding on the beam 40 when the visual sensor is used and when the laser sensor is used. The focus is sufficient and high-precision measurement is possible. The method of exchanging the laser sensor and the visual sensor is not limited to the method using the slider, and the angle of the image capturing camera 36 can be changed so that the image capturing camera 36 can project the light projecting position of the laser projector and the welding position of the welding torch. Can be selectively photographed. In this case, since the distance between the photographing position and the image photographing camera 36 changes, it is desirable to use a variable focus.

  Moreover, in the said embodiment, although the dice filter set was used, the method of replacing the filter for laser sensors and the filter for visual sensors is not limited to this.

The perspective view which shows the state which uses embodiment of this invention as a laser sensor The perspective view which shows the state similarly used as a visual sensor Flow chart showing the processing procedure of the embodiment Schematic diagram of laser beam cut image of V-shaped groove in the embodiment Similarly, a schematic diagram of a laser beam cut image of a temporary bead The figure which similarly shows an example of welding control The figure which shows the other example of welding control similarly The figure which shows the further another example of welding control similarly The figure which shows the method of the welding control in the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... To-be-welded object 11, 11 '... Groove 12, 12' ... Molten pool 20 ... Welding head 22 ... Welding torch 24 ... Welding electrode 26 ... Welding condition control apparatus 30 ... Laser projector 30S ... Laser slit light for illumination 31 ... Dice filter set 32 ... Laser sensor filter 34 ... Visual sensor filter 36 ... Image capturing camera 38 ... Image processing device 40 ... Beam 42 ... Slider 52 ... Compound sensing system controller

Claims (8)

Using a composite sensing system of at least a laser projector, a laser sensor filter and an image capturing camera, and a visual sensor composed of at least a visual sensor filter and an image capturing camera for an object to be welded,
An automatic welding control method comprising performing welding control by causing a visual sensor and a laser sensor to function alternately during welding.   2. The automatic welding control method according to claim 1, wherein the composite sensing system includes a single image capturing camera in which a filter for a laser sensor and a filter for a visual sensor are interchangeably functioned.   A state in which the composite sensing system is used as a laser sensor in a state in which the welding arc is expected to be measured, sensor information is measured and stored in a welding in-process, welding is performed by feedforward control based on the information, and a welding arc is expected The automatic welding according to claim 1, wherein the automatic welding is used as a visual sensor, detects a change in welding state generated during welding by welding in-process, and performs feedback control in real time based on the information. Control method.   The change in the welding situation that occurred during the welding is a gap in the groove tracing of the welding torch, and this deviation is detected by a change in the positional relationship between the welding electrode and the molten pool, which is visual sensor information, and feedback in real time. The automatic welding control method according to claim 3, wherein control is performed.   The change in the welding situation that occurred during the welding is a change in the appropriate amount of welding required at the time of the first layer welding, and the welding amount is added based on the height change of the weld pool at the time of the first layer welding, which is visual sensor information. 4. The automatic welding control method according to claim 3, wherein a correct correction amount is obtained and feedback control is performed in real time. A laser sensor comprising at least a laser projector, a filter for a laser sensor, and an image capturing camera;
A visual sensor comprising at least a filter for a visual sensor and an image capturing camera;
Means for causing the visual sensor and the laser sensor to function alternately in a state where a welding arc is expected immediately before welding and a state where a welding arc is expected during welding;
An image processing device for calculating welding control data from images obtained by the laser sensor and the visual sensor;
An automatic welding machine with a welding torch,
Means for controlling the automatic welder based on the welding control data;
An automatic welding apparatus comprising:   7. The automatic welding apparatus according to claim 6, further comprising a single image capturing camera in which the filter for the laser sensor and the filter for the visual sensor function so as to be interchangeable.   The image photographing camera, the laser projector, and the welding torch are all attached to the same beam, and the image photographing camera is capable of photographing the projection position of the laser projector and the welding position of the welding torch. The automatic welding apparatus according to claim 6 or 7.

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